the
organ exercised, and must be proportioned to the strength of the organ,
if true development is to be attained.

In order to understand this in so far as it bears upon the aims which we
should set before us in the physical education of the child, it is
necessary that we should understand what modern physiological psychology
has to teach us of the nature of the nervous system.

If the reader will look back to an earlier chapter,[26] he will find
that education was defined as the process by which experiences are
acquired and organised in order that they may render the performance of
future action more efficient, or alternatively it is the process by
which systems of means are formed, organised, and established for the
attainment of various ends of felt value. The establishment of these
systems of means is only possible because in the human infant the
nervous system is relatively unformed at birth, is relatively plastic,
and so is capable of being organised in such and such a definite manner.
On the other hand, in many animals the nervous system of each is
definitely formed at birth; it is so organised that experience does
little to add to or aid in its further development. Now, while the
nervous system of the child at birth is not so definitely organised as
that of many animals, yet on the other hand it is not wholly plastic,
wholly unformed, so that, as many psychologists and educationalists once
believed, it can be moulded into any shape we please.

Rather, we have to conceive of the nervous system of the human infant as
made up of a series of systems at different degrees of development and
with varying degrees of organisation.[27] Some centres, as _e.g._ those
which have to do with the regulation of certain reflex and automatic
actions, start at once into full functional activity; others, as _e.g._
those which have to do with purely intellectual functions, are
relatively unformed and unorganised at birth, and become organised as
the result of conscious effort, as the result of an educational process,
as the result of acquiring, organising, and establishing experiences for
the attainment of ends of acquired value.

Between the systems at the lowest level and those at the highest we have
centres of varying degrees of organisation at birth. Moreover, these
centres of the middle level reach their full maturity at different
rates. The centres, _e.g._, which have to do with the co-ordination of
hand and eye and with